1. Field of the Invention
The present invention relates to a method of manufacturing an ink jet head, as well as the ink jet head.
2. Discussion of the Background
Reference will first be made to the construction of a conventional ink jet head. FIG. 12(A) is a perspective view showing an example of a conventional ink jet head and FIG. 12(B) is an explanatory diagram showing an arrangement of nozzles.
The conventional ink jet head illustrated therein, which is indicated at H1, is made up of a head substrate 101 formed with plural grooves (to be described later) for the supply of ink, a nozzle plate 102 bonded to a front end face of the head substrate 101, a channel-formed member 103 bonded to one side of the head substrate 101, a top plate 104 which closes a top side of the channel-formed member 103, and an ink supply member 105 bonded to the top plate 104.
The channel-formed member 103, which has a frame-like shape, is for internally intercommunicating the plural grooves formed in the head substrate 101. The head substrate 101 is formed by a piezoelectric member and aside wall is formed between adjacent ones of the plural grooves formed in the head substrate 101, with an electrode to be described later being formed inside each groove.
By applying voltage to the electrode, the side walls located on both sides of the groove are deformed and the volume of the groove changes at high speed. The ink jet head H1 is constructed such that ink is fed into the groove during expansion of the groove volume, while during contraction of the groove volume, the ink present inside the groove is ejected through an associated one of nozzles 106 formed in the nozzle plate 102. In the example of the illustrated ink jet head H1, an actuator for ejecting ink is constituted by both a piezoelectric material as the material of substrates 107 and 108 and electrodes which apply voltage to the piezoelectric material.
Next, a detailed construction of the conventional inkjet head H1, as well as a manufacturing process for the head, will be described below. FIGS. 13 to 20 are explanatory diagrams showing an ink jet head manufacturing process.
First, as shown in FIG. 13, there are provided two substrates 107 and 108 formed of a piezoelectric material polarized in the plate thickness direction and then the substrates are bonded together so as to be opposite to each other in the direction of polarization to form a laminate substrate 109.
Next, as shown in FIG. 14, plural grooves 110 are formed in one side of the substrate 108 so as to span the bonded surfaces of the two substrates 107 and 108, whereby there is formed a head substrate 101 having plural grooves 110 and side walls 111 as partition walls between adjacent grooves 110. The grooves 110 can be formed easily by a grinding work which uses, for example, a diamond wheel of a dicing saw for cutting IC wafer. The size of each groove 110 is determined according to the specification of the ink jet head H1.
Then, as shown in FIG. 15, electrodes 112 are formed on inner surfaces of the grooves 110, and wiring patterns 113 connected respectively to the electrodes 112 are formed on one side of the head substrate 101. The electrodes 112 and the wiring patterns 113 are formed by-an electroless plating method using a wet process.
Subsequently, as shown in FIG. 16, a frame-like channel-formed member 103 formed with a channel 103a at its center is bonded to one side of the head substrate 101.
Next, as shown in FIG. 17, the head substrate 101 and the channel-formed member 103 are cut off at the front-end side of the grooves 110. This cutting work is performed for making the grooves 110 uniform in length. Indicated at 114 is a cut piece resulting from this cutting work.
Then, as shown in FIG. 18, a nozzle plate 102 is bonded to the front ends of the head substrate 101 and the channel-formed member 103, and nozzles 106 are formed in the nozzle plate 102.
As subsequent steps, as shown in FIG. 19, a top plate 104 with an ink supply member 105 pre-bonded thereto is bonded to an upper surface of the channel-formed member 103, or as shown in FIG. 20, first the top plate 104 is bonded to the upper surface of the channel-formed member 103 and thereafter the ink supply member 105 is bonded to an ink supply hole 104a formed in the top plate 104.
In case of adopting the method wherein the nozzle plate 102 pre-formed with nozzles 106 is bonded to the head substrate 101, the position where the nozzle plate 102 is bonded must be controlled strictly in order to align the centers of the grooves 110 with the centers of the nozzles 106. However, this work is difficult. Therefore, there sometimes is adopted a method wherein, after the nozzle plate 102 has been bonded to the head substrate 101, plural nozzles 106 are formed in the nozzle plate 102 in alignment with the centers of the grooves 110. In case of adopting this method, there is used either a method wherein with the nozzles 110 kept open, the nozzles 106 are formed from inside the nozzle plate 102, and a method wherein the nozzles 106 are formed from outside the nozzle plate 102. For forming nozzles in the former case or for removing cut chips from the grooves 110 in the nozzle forming work in the latter case, it is necessary that the nozzles 106 be formed before the top plate 104 is bonded to the head substrate 101 (in the state shown in FIG. 18).
Since the top plate 104 is a flat member of a simple shape, it permits a wide selection range of materials having a thermal expansion coefficient equal to that of the head substrate 101. However, as to the ink supply member 105, its material selection range is narrow because it is complicated in structure which is attributable to its relation of connection to an ink supply system and also because a high strength thereof is required. For this reason there often is used a metallic ink supply member 105.
Therefore, even if there is used a thermosetting adhesive in bonding the substrates 107 and 108 with each other, or bonding the head substrate 101 and the channel-formed member 103 with each other, or bonding the channel-formed member 103 and the top plate 104 with each other, there is no fear of warp of those members in the course of hardening of those members.
However, as shown in FIG. 19, in the case where the top plate 104 with the ink supply member 105 pre-bonded thereto is bonded to the channel-formed member 103, heat which reaches 100° C. or so during hardening of the thermosetting adhesive is transferred to the ink supply member 105 from the top plate 104. Since the ink supply member 105 made of metal is higher in thermal expansion coefficient than the top plate 104, it contracts largely while the conducted heat drops to a lower temperature, and pulls the top plate 104 longitudinally from outside to inside. As a result, the top plate 104, which is a thin plate, is curved upward in FIG. 19. Consequently, the channel-formed member 103, head substrate 101 and nozzle plate 102, which are bonded in this order to the top plate 104, are also deformed following the curving of the top plate 104.
Further, as shown in FIG. 20, when the metallic ink supply member 105 is bonded through a thermosetting resin to the top plate 104 bonded onto the channel-formed member 103, the temperature of the ink supply member 105 and that of the top plate 104 rise due to heat which reaches 100° C. or so during hardening of the thermosetting adhesive, and the ink supply member 105 contracts largely while the heat drops to a lower temperature, pulling the top plate 104 longitudinally from outside to inside. As a result, as is the case with FIG. 19, the thin top plate 104 is curved and the channel-formed member 103, head substrate 101 and nozzle plate 102 are also deformed following the curving of the top plate 104.
Thus, no matter which of the methods shown in FIGS. 19 and 20 may be adopted, the nozzles 106 located inside both-end nozzles become misaligned relative to a virtual straight line A which connects the centers of nozzles 106 located at both ends, as shown in FIG. 12(B).
The curing temperature of the thermosetting adhesive differs for example like 120°, 100° C., 80° C., and 60° C., depending on the adhesive selected.
Additionally, in case of fabricating the ink supply member 105, a rise of the manufacturing cost is unavoidable because the selection range of a material having a thermal expansion coefficient equal to that of the head substrate 101 is narrow.